A measure of how effectively electricity is being used in your facility, your Power Factor can be calculated by dividing the Working Power drawn by the Apparent Power employed. A high quotient indicates efficient use, while a low quotient is indicative of the opposite.
A poor Power Factor is costly, both in terms of revenues and wasted energy.
As a result, utility companies often impose monetary penalties upon customers with a low Power Factor to “help them decide” to make improvements with solutions such as Power Factor Correction.
Of course, one must have an understanding of Power Factor Correction to effect this — which is what this article is intended to do.
Working Power vs. Apparent Power
Working Power, expressed in kilowatts (kW), is also referred to as “True” and “Real” power. This is the energy used to perform tasks such as heating, lighting and setting electric motors into motion. These are known as known as resistive loads.
Motors, compressors and ballasts need Working Power to establish the magnetic fields they use to function. However, this is more properly referred to as Reactive Power and is expressed in kilovolt-amperes reactive (kVAr).
Working Power and Reactive Power combined are known as Apparent Power and is expressed as kVA.
Let’s say for example you have a device that runs at 100 kW of Working Power but attaching an Apparent Power meter records its draw at 125 kVa. Dividing the kW by the kVa yields a Power Factor of 80 percent. From this, you can deduce 20 percent of the energy going into that device is being wasted.
Power Factor Correction
Improving the Power Factor maximizes current carrying capacity, increases the amount of voltage reaching your equipment, reduces your power losses and — as a result — lowers your energy bills.
This is often illustrated in correlation to a mug of beer.
The total capacity of the mug (let’s say 16 ounces) is the electricity being drawn. Looking at the mug from the side you can see liquid beer consumes 12 of the available ounces of capacity, while foam consumes the other four. This means 25 percent of the capacity is being wasted.
Tilting the glass to one side and pouring the beer in slowly reduces the accumulation of foam and maximizes the amount of liquid you can get into the mug. Power Factor Correction (PFC) is basically the equivalent of tilting the mug to one side and pouring beer in slowly.
Expressed in electrical terms; placing a high value capacitor across the phase and neutral — close to the load in need of correction — reduces the lagging power factor in inductive loads. This puts Voltage and Current more into phase, which in turn, drives inductive loads more efficiently.
Basically, helping you get more “beer” into the “mug.”
Placement Is Critical
Understanding Power Factor Correction and how it works is key to deploying it to your best advantage. A lack of knowledge in this regard could lead to an over-correction situation, which could result in damage to the system.
If the PFC device is placed right at the electricity’s point of entry, at the distribution point, or directly after a meter, the initial surge that occurs when current is drawn could cause the PFC device to overreact.
To avoid this, it’s crucial to install PFC close to the inductive load. This way, correction will be applied only to the load, as opposed to the entire system — potentially impacting components for which PFC is not an issue.
Properly deployed, PFC can reduce the load your transformers and conductors are tasked with handling, which can deliver enhanced reliability along with significantly reduced costs.
